## Moles and Substances

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George
Posts:17
Joined:Mon Feb 20, 2017 8:53 am
Moles and Substances
Evening guys,

I'am doing an independent assignment at the moment and could use some guidance on a few questions. We have had zero help in class, so we have to do our own research and seek help elsewhere.

I'am just looking for help/advice and to be pointed in the right direction, a few questions are giving me headache, or I'am not confident with some of my answers, so any help is appreciated.

Questions:

1) When asked about how many particles of Hydrogen are in 1 gram of Hydrogen, one student said 6.02 × 1026, but another student said 5.97258 × 1026. Explain the difference of opinion and say who is correct (if any).

2) A lump of Iron weighing 111.7 grams was left in the rain and rusted to make Iron (III) Oxide. When it was weighed again it weighed 150 grams. Calculate how much of the iron reacted with oxygen. Show your working.

3) Given that HCl reacts with NaOH to make NaCl and H2O, what mass of HCl was used to make 29.22 grams of NaCl? Show your working. HCl + NaOH  NaCl + H2O

4) Calculate the mass of CuSO4 needed to make 25 cm3 of a 0.1 mol dm-3 solution.

5) g) A 0.50g sample of potassium (V) iodate, KlO3 is dissolved in water and made up to 250cm3, a 25.0cm3 sample of this solution is added to an excess of Potassium Iodide in Sulphuric acid solution. The reaction is:

1O3- + 5l- + 6H+  3l2 + 3H2O

The Iodine formed requires 20.0cm3 of Sodium thiosulphate solution for titration, the reaction is:

2Na2S2O3 + I2  Na2S4O6 + 2Nal

What is the concentration of the Sodium thiosulphate solution and how many molecules of Sodium thiosulphate is there in 20 cm3 of solution? Explain your answer.

I know it is unethical to just ask for answers, So I'am more than happy with any hints tips you have to set me in the right direction (And if you do answer them, can you explain how you got your answer so I can understand and learn, the assignment will be followed by an open book exam)